Kent

Kent is a large county in southeast England, the part of Enkland which is
closest to the continent.
Both the shortest ferry connection from Dover and the tunnel start in Kent.

The geology is dominated by a huge dome of alpine origin, called Wealden Dome.
The results of different resistance against weathering between the layers are
hills and escarpments.
But the layers are sandstones, marls and clays.
There is no limestone, which would allow cave formation, so the county has no
natural caves.
But the Cretaceous chalk on top of the stack, which is completely eroded in the
center of the structure, remains at the northern and southern rims.
This chalk forms the famous cliffs of Dover.
Being rather soft it is easily excavated for cellars and various other uses.
There are numerous subterranea in Kent which were dug in the chalk.
Except for the channel tunnel all listed site are of this categroy.

Kent has a coal mining history, there were numerous collieries.
Today almost nothing remains of the various mines, only a few old buildings.
There is no museum dedicated to the coal mining and no show mine, but there is
the Coalfields Heritage Initiative Kent who created a trail called Miner's Way
Trail.